What is Yellow Pig Day? If you are to believe Wikipedia, which of course, I am, Yellow Pig Day originated in the early 1960s when two Princeton math students, Michael Spivak and David C. Kelly, spent hours obsessively analyzing the number 17. Probably because the lack of sleep caused the two to go temporarily guano loco*, they invented (or more likely, hallucinated) the 17-toed, 17-teethed, 17-eyelashed, 17-etc. yellow pig. As is usually the case with college students, (yes even geeky mathematicians) a party was born. Now Yellow Pig Day is an important part of the academic calendar, and is celebrated with cake, carols, parades and general revelry.